1. Field of the Invention
This invention relates to a process for dyeing a series of successive garments with a vat dye. The process includes the steps of rapidly impregnating each garment at or near ambient temperature with an aqueous solution of a vat dye and quickly oxidizing essentially all of the vat dye impregnated into the garment. In a preferred embodiment, those two steps of dye impregnation and oxidation occur in less than about ten minutes.
2. Description of the Prior Art
Indigo dye is a type of vat dye that has been known for centuries. Being a vat dye, indigo is normally insoluble in water, but is easily reduced to an amber colored water-solub1e form. This soluble form is used to impregnate and dye fibers; subsequent oxidation insolubilizes the dye and produces the final color.
The use of indigo to dye cotton textiles in raw stock, yarn, and fabric forms is well known. See, e.g., U.S. Pat. Nos. 3,457,022; 4,283,194; and 4,342,565; and Canadian Patent No. 1,098,258. These methods are lengthy and consume large amounts of energy by their use of elevated dyeing or oxidation temperatures.
For example, U.S. Pat. No. 3,457,022 describes a process of dyeing cotton yarn wherein indigo is first applied at a temperature of from about 65.degree. to 85.degree. C. The indigo is subsequently oxidized by "skying" the yarn. "Skying", or oxidation by exposure to air, is a lengthy procedure that can take several minutes for yarn lengths and on the order of hours for fabric or garments to produce the final desired color.
U.S. Pat. Nos. 4,283,194 and 4,342,565 disclose a method of dyeing relatively dry cotton yarns and fabrics wherein the indigo dye vat is maintained at a temperature of from about 55.degree. to 90.degree. C. After dyeing, the indigo dye is oxidized by skying or chemically by use of an oxygen donor such as peroxide. No details are given of the chemical oxidation technique.
Canadian Patent No. 1,098,258 discloses a method for dyeing wet cotton yarn. The yarn is passed in sheet form through a wash box so as to treat the yarn with a wetting agent at about 95.degree. C. With a moisture content of about 50% based on the weight of the yarn, the yarn is cooled to about 20.degree. to 25.degree. C. and fed to at least one indigo dye bath maintained at approximately the same temperature as the cooled yarn. The yarn sheet is subsequently conveyed to an oxidizing tank maintained at about 43.degree. C. wherein the indigo dye is fixed in the yarn by a chemical oxidation agent such as sodium bichromate, sodium perborate, hydrogen peroxide, or mixtures thereof. The patent discloses that the preferred speed of the yarn sheet through the system is 50 yard per minutes, or about twice the speed of dyeing yarn in rope form using the skying method of oxidizing.
There are several outstanding advantages to dyeing garments with indigo dye as compared to making garments from indigo-dyed yarns or fabric.
First, dyeing garments provides cost savings based on rapid production rates, low capital outlays, and effective inventory control. Second, dyeing garments provides for ease of operation as the labor intensive steps of warp beam make-up and yarn quilling processes are no longer necessary. Third, dyeing garments more easily achieves the color-coordinated clothing products that result from dyeing garments that contain both knit and woven patterns or that comprise jacquard patterns of different types of yarns.
These and other advantages of the process of the present invention will be apparent from the following detailed description of the invention.